If you're feeling good about the market, you're not alone. Take my hand as we go over some of this week's more uplifting headlines.

1. It's time to trade
Leave it to a little market volatility to awaken investors into shaking up their portfolios. E*TRADE (NASDAQ:ETFC) and TD AMERITRADE (NASDAQ:AMTD) announced an uptick in brokerage activity last month, with daily average revenue trades coming through with sequential 21% and 22% pops respectively over December's numbers.

It is comforting to see the discount brokers come through after a bumpy close to 2009. Between low interest rates challenging money markets to remain positive and recent price cuts, discounters need to maintain a healthy flow of buys and sells to bring home the bacon.

As long as January wasn't just a case of disgruntled investors cashing out for good -- and recent gains seem to suggest that this is not the case -- the industry will be just fine.

2. Life in a vacuum
's (NASDAQ:IRBT) Roomba is an overseas hit. The vacuuming automatons experienced a 31% spike in international sales during the holiday quarter, helping propel iRobot's top line 12% higher.

Spotty profitability has held iRobot's stock back in the past, but it had no problem staying in the black this time around. The maker of consumer and military robotics earned a quarterly profit of $0.20 a share, well ahead of Wall Street's $0.16 a share target.

Can it be? Are we finally at the point in iRobot's life stage where we don't have to send in a bomb-sniffing PackBot to handle its quarterly reports, fearing that they will blow up on us?

3. Left of the decimal
It took 17 months of living to the right of the decimal, but Sirius XM Radio (NASDAQ:SIRI) is finally trading in the single digits.

Shares of the satellite radio operator finally traded above the $1 mark on Wednesday. They haven't look back ever since.

Breaking the buck is more than just a round number. Nasdaq threatened a delisting if Sirius XM didn't get its stock up to the $1 minimum listing requirement. The media giant isn't out of the woods just yet. It needs to close at $1 or higher for 10 consecutive trading days.

Given Sirius XM's historical volatility, that's easier said than done. Still, did anyone really think that Nasdaq would delist one of its most actively traded companies?

4. Deere hunter
"Nothing runs like a Deere" is the slogan at Deere & Co. (NYSE:DE). It certainly fit this week when the farming equipment maker came through with a quarterly profit of $0.57 a share.

Analysts were bracing for net income of $0.19 a share, well short of the $0.48 a share it posted a year earlier. Deere came through with stellar bottom-line results, despite a 6% decline in revenue.

Cost-cutting is clearly the key at Deere, allowing the company to juice its margins. If this is what Deere can do now, just imagine what will happen when demand for its agricultural gear returns.

5. Following the Hurd
It was a tale of two PCs as Hewlett-Packard (NYSE:HPQ) and Dell (NASDAQ:DELL) posted quarterly results a day apart.

HP held up well, with revenue and earnings climbing 8% and 28%, respectively. In other words, margins expanded nicely. It's a sharp contrast from Dell's numbers last night. Dell surprised analysts with a sharp 11% top-line advance, but then squandered the lovefest by posting a 2% decline in year-over-year adjusted net income.

Both companies have spent the past few quarters cutting corporate overhead, so bottom-line growth should have been explosive now that sales are coming through.

Sadly, only HP delivered on that end, and that explains Dell's lower open this morning.

iRobot is a Motley Fool Rule Breakers pick. Try any of our Foolish newsletter services, free for 30 days.

Longtime Fool contributor Rick Munarriz is an optimist at every turn. He does not own shares in any of the stocks in this story. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.