I also have a Harbor freight Aluminum motorcycle lift and I like it because I can get the bike off the ground to a comfortable height to work on the bike and even under it if I have to. The wooden lift mentioned would work OK but there are times when you need more height, especially if you have a bad back like I do.
it's definatly worth getting a jack, it makes serivce so much easier and safe, they aren't that expensive from Sears Craftsman either.
+1 to that. Plus it saves money in the long run. When you can safely get the bike and both tires off of the ground it's cheaper to replace the tires. To replace tires at most shops it's around $350 when all is said and done. Cycle Gear does it for $200 but doesn't remove the wheels (Price quotes in my area). If you remove the wheels yourself and take it their, then you've saved more than the price of the jack in the first use. I wouldn't trust my $$$ bike to the stability of a 2x4.