I love my Tippmann, but I gotta agree w/ Greenwood. There's a LOT to be said for holding a project with both hands and sewing instead of "hold...pull half way....position....hold...reposition...hold...stitch". Do I regret the purchase of my Boss? Not a bit. I use it as my portable machine (really, it's the only one I have), and set up at the store I sell through. And, you'll not likely be able to take a powered machine to a show with you. But....being able to set the needle once and just start sewing....oh, sweetness. I'm saving up (still) for a Cobra 4, and will keep the Boss. There's some things that it just does better, IMO. Other things, like long runs.....get a motor.
If you do decide on the Boss, definitely get at least one additional foot...I like the center foot, but YMMV. Also get the edge guide. I don't have it yet but could have used it on many projects. I also use the stirrup plate, but for sheathes and such, it's not such a big deal. If you like big thread, look at using 346 thread top and bottom with a 250 needle. If you use one size smaller on the bottom, use a 230 needle, and a cordless drill because you'll be winding bobbins pretty frequently.
Also, spend some time on here reading about the issues that folks have had with them. One of the better ones for diagnosing stitching issues is by Particle, and titled "let's see the back sides.....", talking about the back side stitches of projects. There's a lot of really useful info in that thread on what to look for and how to adjust things. http://leatherworker.net/forum/index.php?showtopic=22058&st=15, thank you Denster and Dwight.