It won't shut down test in low dosages, however I'd guess if you took enough of it over time you may suppress HPTA. Fact is it is a very mild steroid and you won't get massive muscle gains off of it. It primarily stimulates the CNS system which is why you get a lot of strength from it. It will add mass, but it adds it slower than most other steroids because it is so mild.
Ounce for ounce it probably is the best steroid. Many people rate steroids purely by effectiveness with no regards to side effects. Personally I'd rather gain 10 lbs a cycle with no side effects and no need for ancillary drugs(clomid, arimidex, etc..). There is no telling what those drugs may do over the long term. Also I believe it would be easy to keep fat in check using anavar because of it's effect on fat stores.
Your average steroid user wants fast and noticeable gains so they will shun most steroids that do not give this. Because Anavar results are very slow they right it off as a shitty steroid. Even though a good portion of weight that is gained from a cycle is water, people still like to believe that they're making awesome gains. When you gain 10lbs the first week of Dbol of course most of it is water. I see many people on this board that get so excited over this fact, even though they should know it's temporary weight.
Personally I will be doing a cycle of test this fall and will probably stack it with anavar and EQ. The anavar I'm theorizing will make it easier to gain LBM without fat. The EQ should help this as well along with giving me more strength and vascularity.