I've been going through pretty much the same exercise looking for a decent PE for almost two years. Our requirements were for a PE device that had between 12-24 ports (in a perfect world, mixed mode 10/100/1000 copper + SFP), 10G uplinks, EoMPLS, MPLS VPN, DHCP server, port-protect/UNI (or similar) capabilities, DC power and a small footprint (1RU)
Of all the ones we looked at (Juniper, Cisco, Extreme, Brocade, MRV, Alcatel) initially, MRV was the only contender. The rest either didn't have a product, or their offering didn't meet various points within our criteria.
As such, we bought a bunch of MRVs in early 2009 and after four months of trial and error, we yanked every single one out of the network. From a physical perspective, the box was perfect. Port density was perfect, mixed-mode ports, promised a 10G uplink product soon, size was perfect, power was perfect, we thought we had it nailed. Unfortunately there are no words to describe how terrible the software was. The CLI took a little getting used to, which is pretty much par for the course when you're dealing with a new vendor, but the code itself was just absolutely broken, everywhere. Duplex issues, LDP constantly crashing taking the box with it, OSPF issues, the list went on and on. To their credit, they flew engineers up from the US and they were quite committed to making stuff work, but at the end of the day, they just couldn't make it go. We pulled the plug in May 2009 and I haven't heard a thing about their product since then, so maybe they've got it all together.
While meeting with Juniper a few months later about a different project, they said they had a product that might fit our needs. The EX4200. As such, we had a few of these loaned to our lab for a few months to put through their paces, from a features and interoperability perspective. They work[1] and they seem to work well. The show stopper was provisioning[1] and size. The box is massive, albeit it is still 1U.
[1] (I'm not a Juniper guy, so my recollection on specific terms and jargon may be a bit off kilter) they only support ccc, which makes provisioning an absolute nightmare. From my experience with Cisco and MRV, you only have to configure the EoMPLS vc. On the EX4200, you have to create the LSPs as well. To get a ccc working, the JunOS code block was far larger and much more involved per vc than the single line Cisco equivalent. To create the LSPs was, I believe, two more equally large sized code blocks. At the end of the day, it was just too involved. We needed something simpler.
About the same time that we started to evaluate the EX4200, Cisco had pitched us on their (then alpha) Whales platform. It looked promising (MRV still had the best form factor) and we expressed our interest in getting a beta unit in as soon as we were able to. This is now known as the ME3600 and ME3800 platform and we've been testing a beta unit in our lab for the past few months. This is the platform we have chosen. It's not perfect, but our gripes have more to do with form factor (it's 1RU, but it's a bit deeper than what we'd like) and port densities (no mixed mode ports) than software or features. We've been pretty pleased with it's feature set and performance, but this hasn't seen any real world action, so who knows how that will turn out.
If you're asking more about a P router or P/PE hybrid, we've also just ordered a few ASR9000s under try-and-buy as P/PEs to close up the chains of ME3600s that will start to be deployed in our remote sites. A Juniper MX would certainly work well here too, and it seems to interoperate rather well with the ME3600s, so that's certainly an option, but for us, we think it will work more in our favor to go with the ASRs in the core, but if not, we'd ship them back under the try-and-buy and get Junipers instead.
Hope that helps.
