The only downfall to using it would be that you would still need to retexture the model and delete unneeded faces in another modeller.
Sayeth the newbie modeler
Now, there are some exporters, IIRC, that will handle Hammer output, and turn them into .3DS or .LWO files. I remember somebody sending me one of those one time (some guy made a spaceship with Hammer) and he said in his email, "gosh, it looks great in Hammer, but when I tried to import it into the game engine, it looked terrible!)
Here are the reasons why:
1. Hammer expects multitexturing. Spring does not support multitexturing (this is actually a strike against Spring, but it's a very minor one- we can use texture up to 4096*4096 if we like watching slide shows). So, in order to use Hammer content in Spring, you're going to have to learn how to uvmap and texture anyhow! Might as well use a good application in the first place.
2. Hammer does not understand welding (Wings doesn't do it quite the same way as Spring, but you can address this in UpSpring very easily). So, you're missing an important part of making good models, which is using smoothing groups, etc.
3. Hammer export, IIRC, put literally hundreds of cutting faces into the interior of the model, due to the way that Hammer works (it is a modeling environment designed for a 3D engine that expects "rooms" and optimizes appropriately, which is completely different than what Spring is doing).
Basically, I can see why people try out Hammer, and think, "hey, I'm a newbie modeler, and this feels easy and comfortable for me". I've used Hammer before, and it's pretty intuitive to use. However, from the standpoint of making things for Spring, it sucks. Gotta use the right tools for the job.
Now, is Wings the only cheap tool available? No, there's always
Milkshape3D (clunkier modeling interface, but it works better for a few things than Wings and has more tools, but it costs a little bit) and Gmax (fairly good modeling / texturing tools, is free, but you have to
go grab an exporter for the Quake 3 format, and then buy a copy of Milkshape3D to export to 3DS).
If you're a student at a university, I strongly suggest either getting Rhino3D 3.0, at student discount rates, or the latest version of 3DS, both of which are made available to students at a fairly low price. I love Rhino3D, myself- it's intuitive, very easy to learn, but it includes very, very powerful modeling tools, for getting the tough jobs done, fast and accurately.
In short, if I were you, I wouldn't waste any more time using the wrong tools for the job- you're just going to become very bitter and disappointed, when you realize that you're making neat-looking models that are utterly useless in Spring, and you can save yourself much grief by learning another tool now. Wings is the favorite around here, because it's free and the uvmapping tools are really pretty good (I use 'em, for weird shapes, but I mainly use UVMapper Pro).