Hmm...
The ones I still have in service now :
Win2000 Professional SP4
WinXP SP1
Win98SE
Win98
WinNT SP6 for Alpha
Win95 OSR1/SP1
Win95A
I presently like the Win2000 the most (running on my main Gaming rig)
(very volunerable OS by now however, requiring very strict and solid Firewalling, constant patching, and a permanent, keen eye on it
)
It feels like a bit of a resource hog (compared to the slick '98, but given enough RAM, it runs 'as good as it gets' IMHO)
The 98/98SE Systems I mostly liked for their ease of use; very quick to setup or troubleshoot, and a very straight-forward plus backwards compatible OS (and almost free of Spyware).
I think those gave me the least Troubles of all M$ OS'es in the past.
The 95 Systems I did setup, because it was dirt cheap to pick up mostly; still gets the Job done nicely, though, even on fairly high-end Hardware actually
(when was the last time you've seen a Windows completely boot in less than 8 Seconds from scratch ?)
WinNT is quite an immobile and unflexible OS, but once setup, gives the impression that it is determined to run until the end of days. It feels like the only thing that could stop it from running, would be the failure of the Hardware it runs on after like 15 years
XP I dislike the most, but the Notebook it runs on gave me a good fight, not accepting any other OS after 2 weeks of fierce battle
(I intend to either sell it, or try Win2000 on it again one day, but it will be the first and last WinXP Installation I ever did in my Network
)
For security reasons, it has been almost isolated from the rest of the Network, setup to perform only very limited actions or connections.
Very resource unfriendly, almost feels like bloatware, until you strip it of almost all its "Features".
Generally, rated as "untrustworthy" Software, requiring massive intervention, Firewalling and 'cleansing' before first use.
Connecting a default WinXP installation to the Internet is widely regarded as a practically applied "digital suicide".
----------------
Within the next months, however, Linux Installations will have taken all their places, with the Exception of one Notebook and the Gaming rig.
(Presently it's 60% Linux or Unix vs. 40% Windows in the Network, with Linux gaining more and more momentum
)