VDS is better than Howard was for a reason mentioned earlier: Command of area. Howard had no major command of the area however VDS has nailed it. He communicates excellently with the defence and manages them well. When Foster/Tomasz are in goal, I don't have as much faith for that reason alone - the defenders suddenly don't seem as well managed. I don't think Ben or Tomasz like to yell at Rio or Vidic, but they need to be able to do that without a second's thought, and with authority at the same time. Not sure that happens with Foster/Tomasz and don't think it happened with Howard, either. Certainly not as well as it happens with VDS, anyway. Reflexes are one thing, but a very intelligent brain capable of organising the defence well is arguably just as valuable, if not more so.
I'd say Lehmann was a pretty good keeper, certainly better than most mentioned in this thread recently enough, although near the end of his playing days for Arsenal he suffered - although that could just as well be pointed at the defence he worked behind, not sure...
EDIT: As for Almunia, I wouldn't go as far as to say he's crap. A basic PL keeper, although I wouldn't say he's a star player for a team of Arsenal's history.