Since the launch of the original Surface RT in 2012, Microsoft (NASDAQ:MSFT) has had a bold vision for the hybrid computer.

The device was meant to be more than just a tablet with a keyboard added to it. Third-party keyboards had long been available for Apple (NASDAQ:AAPL) iPads, and so have cases that integrate the typing devices into the tablet, making it a quasi laptop.

With Surface, Microsoft wanted to go further and build a true hybrid -- one that works as well a high-end tablet and a high-end laptop. It was an aggressive goal and one that early versions of the device did not quite live up to. The latest models of the Surface, the Pro 3 and the 3, come closer and the company boldly calls the higher-end Pro model "the tablet that can replace your laptop," in commercials like the one below.

Source: Microsoft

It could replace your laptop, but after playing with both models, it's probably not going to work that way for most people. The new Surface models are excellent tablets with an improved version of the keyboard "Type" cover that the company has pioneered. They can act in a laptop-like fashion in a pinch, but it still feels like a compromise.

It's like eating vegan meat or gluten-free pizza. The recipes have gotten much better and you may not mind them, but it's no substitute for the real thing. 

Surface 3 vs. Pro 3
The company has marketed the Pro 3 as its top-tier product and it sells the 3 as an affordable compromise. In playing with both, I found the two machines similar and at times the larger size of the high-end model actually made it less comfortable to use. The Pro's better processing power might matter for users attempting to do resource-heavy things, but for Web browsing and typing, I found the two machines pretty interchangeable.

For users who don't need the faster processor and biggers screen of the Pro, the 10.8-inch screen 3 may actually be a better value. It starts at $499 for the version with 2GB of RAM and 64GB of storage compared to $799 for a 4GB/64GB Pro with a 12-inch display. The higher-end machine does include the new Surface Pen which costs $49.99 on its own.

The Pro also has a kickstand with infinite positions while the 3 is limited to three (up from one on the original version). That gives the professional model a slight edge, but for most uses, three settings is more than enough.

A major drawback for the line as a whole is that neither device comes with the Type cover, which at $129.99, pushes up the price of either machine over comparable iPads and into the territory of some very good laptops.  

Why can't it replace your laptop?
Both Surface models can perform the functions of a laptop and a clever change to the Type cover allows it to be fixed into place which eliminates side-to-side movement allowing the devices to actually be used on your lap. That clears up a big problem in the earlier iterations of the hybrid, but it does not help it cross the divide from being a tablet with a good keyboard to being a laptop.

The Type cover is better. I own the version and the now-abandoned Touch model and found writing on them hard to do. Over extensive use, they never grew comfortable and while the Touch was fine for answering email or typing in Web URLS, I did not want to do any real work on it. The new version improves the key feel but it's still just good for a tablet -- maybe the equal of some low-end laptops, but not a replacement for a decent one (or a MacBook Air as some ads suggest).

It's still pretty good
The new Surface models work well in situations where you need some laptop functionality but mostly want a tablet. They would certainly make ideal travel machines for people willing to sacrifice a bit in order to not carry two devices. As someone who uses a laptop all day (a Dell Inspiron with a 15.6-inch display and a MacBook Air depending upon my location) with heavy keyboard work, switching to a Surface would be too big a sacrifice.

Aside from the deficiencies in the keyboard, it's also difficult to use the Surface as a laptop when not on a hard service. The new keyboard locking position helps, but it does not fix the problem.

Surface makes sense for some people, but for most, it's just not a good enough laptop to make it a true replacement for even a decent traditional, nonhybrid device. It could replace your laptop -- you just, in most cases, wouldn't want it to.