Now, that's more like it. After a number of rumors -- some good, some bad -- regarding Nokia's (NOK -0.27%) Lumia smartphone sales results, CEO Stephen Elop finally gave shareholders something to hold onto. Nokia's preliminary earnings announcement on Jan. 10 was sweet music to the ears of its fans, who've been waiting for a sign that Elop's strategic business shift is taking hold.

Though still early in the game, based on early returns, Nokia's decision to move full steam ahead in the Microsoft (MSFT -2.45%) Windows 8 direction appears to be working. Smartphone sales results, along with some great news out of the sometimes-neglected Nokia Siemens Networks, drove Nokia's share price through the roof yesterday, and rightfully so. But after 20% appreciation in a day, and over 133% the past six months, is Nokia's share price getting ahead of itself?

First, the good news
The question everyone wants answered heading into Nokia's Jan. 24 earnings call is "How are the Lumias doing?" In addition to Lumia sales, results from Nokia's line of Asha phones, the introduction of its mid-level 620, and even some of those old-school phones running its Symbian OS, all added up to a solid Q4. Total mobile phone sales were just shy of 80 million for Nokia's recent quarter, of which 9.3 million were Asha full-touch smartphones.

Of the 15.9 million smartphones Nokia sold in Q4 of 2012, 4.4 million of the units were Lumia phones running Windows 8, which handily beats expectations. The Lumia results are also a win for Microsoft, as concerns about widespread adoption of Windows 8 are becoming moot. From Nokia's perspective, Elop put it this way, "We focused on our priorities and as a result we sold a total of 14 million Asha smartphones and Lumia smartphones while managing our costs efficiently, and Nokia Siemens Networks delivered yet another very good quarter."

There are two things Nokia proponents should take from Elop's statement, beyond the solid Asha and Lumia sales for the quarter: (1) Nokia's concerted cost-cutting efforts, something Elop focused on in 2012, are beginning to pay off across multiple business units. (2) Nokia Siemens is growing and generating a nice little profit, and continues to provide Nokia, and Elop, time to execute its aggressive smartphone plans.

All those Lumia and Asha sales drove yesterday's share-price pop, but Nokia's device and services (phones, primarily) unit also sold 80 million phones and it appears it will already generate a positive operating margin in Q4, possibly as high as 2%, according to Elop.

Reasons for caution
Smartphone sales, strong results from Siemens, and positive cost-cutting efforts warrant Nokia's positive buying spree yesterday. But Elop's preliminary Q4 announcement wasn't all wine and roses. The first quarter of 2013, according to Elop, will be pressured by "seasonality and competitive environment," negatively impacting the profitability of its devices and services unit.

And while selling 4.4 million Lumia units is an outstanding result in Q4, beating Nokia's own estimates, it should be put into perspective. Samsung just reported selling 62 million Galaxy phones in Q4. Google's Nexus phone lineup appears to be doing well since its release  last year; tracking over a 1 million units sold right out of the gate, And Google's Android OS continues to dominate the world's smartphone operating systems.

Clearly, Nokia is just getting started, so taking significant smartphone market share from the likes of Samsung, Apple, and Google, won't happen overnight. It's still important, however, to recognize the size of the hill Nokia has to climb prior to making your investment decision, one way or the other.

It's the guidance for Q1 of 2013 that may have some itchy Nokia shareholders, particularly after enjoying its 133% jump in value for the past six months, thinking about taking profits. It's tough to blame the line of reasoning: Doubling your investment in six months will get most anyone thinking about cashing out. But before placing your Nokia sell order, here are a couple of additional considerations.

Should I stay, or should I go?
Exceeding Lumia sales expectations is a huge win for Nokia, make no mistake. But what makes Nokia a sound mid- to long-term growth and income investment opportunity goes beyond yesterday's announcement. It wasn't long ago that Elop alluded to expanding Nokia's relationship with Verizon to include selling Lumias, just as AT&T does. Add the potential sales volume Verizon offers with China Mobile agreeing to subsidize Lumias for its 700 million customers, and Nokia's 4.4 million Lumia units is just the beginning.

Though not huge in and of itself, a new deal with Avanade will help Nokia expand in the enterprise market, as more employers allow personal smartphones in the workplace. Enterprise computing is expected to be an area of growth in 2013, according to Gartner, and even a small piece of the enterprise pie is a positive for Nokia. A profitable Siemens Network, strong balance sheet, a 5.6% dividend yield, and its outstanding patent portfolio, will keep Nokia moving in the right direction for years to come.

Nokia shareholders with a mid- to long-term investment time horizon shouldn't give up yet. Nokia's return to prominence is just getting started.