Carbide won't take an edge as sharp as high speed steel will. It's great for roughing, and you can take off a lot more material with each pass, but if you want a good pre-sanding finish, especially on something like acrylic, you want HSS.
I bought a $33 set of indexable carbide tools for my metal lathe, but have been getting better results on metals and plastics from a $5 set of assorted HSS bits bought from Harbor Freight.
If you want the best of both worlds, buy the carbide tools for which there are also HSS inserts.
The inserts for the 5 piece indexable sets are normally C-5for steel 0r C-2 which is primarily for cast Iron, These work great if you touch them up with a diamond wheel, neither of these is available in either Micro grain or Nano grain in a C-3 grade equivalent these will take as keen an edge as HSS. I also have to agree with KenV about the Thompson tools A11 is an excellent material for turning tools, "IF THEY ARE HEAT TREATED PROPERLY" Doug has about the best there is, I have also made a few Carbide tools, Called the Woodchuck Pen Pro and a pretty decent Bowl tool and I use them all, the only tool I have any trouble using is a Skew.
I have both sets and find the carbide to be great. I don't know the technique for roughing with it as it seems to take forever to get round. Lately I round with the roughing gouge then take passes from the side to remove material fast then smooth with the uni-tool, going straight to MM.
I would like to see more tutorials on carbide use.
Jorge
Jorge, Keep your tool rest as close as you can get it to your work piece, I round every thing on my lathe before I drill it, I just use a dead center in the headstock, and a live center in the tail.
I promise I will get some tutorials up besides this one,
http://www.youtube.com/watch?v=_g1iqk2R_bc Which really isn't much of a direction as I need to explain what I'm doing, we are finally ahead on tools so as soon as I get caught up on Handles, Oddly enough since the principle is basically the same, I'll try and Video that, I'ts just a big pen, that won't write, but it's still turning with carbide.
I have both and always gravitate to HSS. Could be I just do not know Ho to use the carbide tools, but I get a near perfect finish with a Sharp skew.
About the best I can do on a pen from good wood is start sanding at 400 grit on good acrylics either PR or Alumilite start sanding at 600 if I want to get totally anal I can get by starting at 800 grit. I know some people that say they don't need to sand after a skew, and I believe it, the few times I've been successful with a Skew I've been amazed, I just can't consistently hit that mark, I've heard it said by many turners that the Skew Chisel is the hardest tool to master. I prefer carbide because it's faster for me, I keep trying though. So far the only thing I have found that carbide doesn't work as well on is use as a bowl scraper, I use one tool with an 18mm round razor sharp insert that does come close, but will still pull grain on softer woods.