Extremely happy user of ACDSee 5.0 PowerPack here.
I'd take ACDSee 5.0 over PS Album anyday... no comparison at all, ACDSee is far superior.
You might want to stick with ACDSee 4.0 if your just a casual user however, ACDSee 5.0 has a ton of additional capabilities and features that many won't touch at all. It's also slowly begun to broaden into areas that other applications already cover much more comprehensively.
For me, I really do utilize ACDSee 5's capabilities on a daily basis and absolutely love the applications flexibility. I can understand why others might view it as bloated however.
IrfanView isnt nearly as widely capable as ACDSee but for straight image optimization/viewer/organizer it's pretty close and most of all... Freeware, whereas one has to purchase ACDSee one the trial has expired.
Thumbs+.... is very popular but frankly I don't see how it can at all compare to ACDSee or IrfanView.
Never used IMatch so I really can't comment on it. I'll have to check it out when I have the time.