Yeah,
the SP-303 sure gives you bang for your buck. Stacks of effects, more than enough memory once you get a smart media card, and a passable pattern sequencer for sketching out (very rough) ideas or storing loops you dump from your PC or groovebox. I love my SP-303, and will probably always keep around even if I get a "real" sampler. It's nice and portable and is set up for sweet live triggering/tweaking.
Competitors would be: Korg ES-1,
Yamaha SU-200 (the 700's more of an advanced loop construction tool and out of your price range) or the uhh Zoom Sampletrak. Since we've scratched off the sampletrak after seeing the brand name that leaves us with the Korg and Yamaha.
I pretty much guarantee that anyone comparing the FX between these 3 will see that Roland kills it. Boss has been making top-shelf effects forever, and makes some pretty good choices about what to include (although a highpass and a bandpass filter would have been a nice replacement to the "vinyl sim" and "radio tuning" crap). Roland = 26 FX, Yamaha = 6 FX, Korg = 11. The Roland has 8 note polyphony, yamaha 6, and korg doesn't come out and say on their site.
The korg's sequencer is more familiar, as it's got our beloved TR-X0X step deal, but if you've got any other gear you're probably better off dumping sequences from that. Yamaha has no sequencer, but it does have a "sync all samples" function which theoretically saves you some tweakin bpms individually, but I don't know about you guys, I generally don't load up 6 loops and try and stretch them to the same size.
Anyways, just a quick list of pros and cons as I've seen em. The SP-303 may not be a studio sampler, but it was never intended to be. It's at its best when triggered from a sequencer or live, and is a versatile multi-fx box. Cheers!
-mj-