When one considers how prevalent Clearcase is, I’m amazed there aren’t more Clearcase hate stories. Don’t get me wrong here, I advocate Clearcase and administer this and the other Rational tools. Nobody likes change, and unfortunately some sites adopting clearcase get some person who has no understanding of CM who has just been to a Rational “UCM is the answer” course and then tries to go the full hog with the engineers off the bat.
Do they have problems? Yes, of course they do. Does the software you create have problems? yes, of course it does. This can be said regardless of the tool.
From what I have seen of perforce, I like, but I would miss the version tree and dynamic views in particular far too much. I also haven’t seen perforce reported as an enterprise level implementation, so I would be wary for enterprise level CM.
Regarding the administrative overhead, I’ve been through this. If you take a company where each project has their own implementation of the tool, or worse, a separate tool, they will say they have no admin overheads. Then you investigate and you find that some poor sode is doing some form of admin with the tool. The admin overheads are still there, they’re just hidden.
All of these tools are designed to help solve what can be an extremely complex problem. I have seen companies that allowed developers to copy, paste, add to source control for product variants and then find they have 12 completely different codebases for the same product with no hope of ever bringing it back together again.
As for SortaSafe, well I used it as a developer and kept getting defect regressions because someone else was overwriting my changes. I’ve also encountered a company that found that when S$afe went cacti, they found the backups hadn’t run for 3 months. They had one poor sod working for 6 months trying to manually reconstruct deltas and even then found that they couldn’t reproduce the code for some products. The result, a complete rewrite of the products concerned.
Reliability wise, well, if you’re forking out big bucks you deserve reliability. I have seen Clearcase continue operating without file corruption on hard disks that are dying - on the same stripe. I don’t see any Relational Database system handling this situation too well (including team system).
Do the UCM Guis suck? Yes. Does UCM make assumptions about all files being mergeable? Yes. Can you effectively use the tool if you’re aware of these things? Definitely.
I guess what I’m getting at, is that these tools can be like a gun - regardless of who makes them or the product. I can see a lot of damage being done long term if you used say the one SVN implementation for a company of say 30,000 people, for instance.
Some of the arguments shown here can be ridiculed, but shouldn’t. One thing I do know about all of these tools is that there has been very few technological advances that I have seen since Atria Released Clearcase and Clearcase Multisite. An exception would be SVNs approach to versioning, which I don’t agree with, but it was a good show of lateral thinking, I must say. A lot of the rest of it seems to be the same S*( in a different package IMHO.
One more thing, I would take using Winzip over Sourcesafe any day. At least when you go back your files are in the location they originally were in!
Also, regardless of the tool you will allways have the fanatics and the gripes and so forth. Evaluate and make up your own mind, but don’t just get a junior developer to do the implementation.
In that case, Clearcase is modern, too. 
I believe TFS is nothing more than something similar to Perforce under the covers. The only quote unquote, modern, source control tool I’ve looked at was Accurev and it did just win its second Jolt Award. Most source control will do if you don’t have to worry about process, parallel development, branching off the mainline so to speak, managing an offshore team or collaborating on shared projects. But please don’t try to use a free or RCS-based tool for these more complex problems (like using swiss cheese to hammer in a nail).