The "new" L-Series is nothing more than a re-labeled "SL" series that will replace the SL510, SL410 (hint hint "L412 & L512") If you look at the service manuals, they are the same thing.
The only thing different is that the L's have i3/i5 CPUs, otherwise its the same case, battery, etc as the previous model. The new model Ts are out with i5~i7 CPUs.
"L Series Geared for Professionals" is perhaps somewhat true. In comparison to buying other $600~800 notebooks. Its a very modern looking Thinkpad, but other than the liquid protection system, it has no other ThinkPad features. The ports are excellent with 4 USB ports (one USB is hybrid with the ESATA). The "latch" can go both ways... as a latch does keep the notebook from being opened by accident.
I've taken an SL-510 apart, its nothing close to an R,T,X or W series (everything else). But for the price, the L/SL are the cheapest "thinkpad" you can get with features that are not available on most notebooks, including Dells. Such as internal WAN antennas for Clear, at&t and Verizon. Bloat/junkware not installed.
Features missing from SL/L series compared to "true" Thinkpads.
- Roll-cage. This also makes them more ridged. SL do have some flex.
- Thinkpad Keyboard arrangement. While still a great keyboard, its not ThinkPad.
- No keyboard light (not a biggie, but some of us DO use that feature)
(( Would like to see Thinkpads with true lighted keyboards, like MacbookPro)
- Hard Drive shock-cage.
- Non-Glossy screens. UGH, I wish the SL/L offered that as an option!
- Steal-hinge. Not sure what the SL/L has, but its not the same. Its an IdeaPad design and layout.
The SL/L are no-where near as tough as the other ThinkPads (Edge not included).
An SL with core-2 WAN/CAM is about $800, A R-500 Series with similar config is $900 - but a T-510 with core-i5 is $1050 which is a good speed bump over Core2... so I think the R-Series maybe phased out... since if it was actually upgraded to the newer THinkPad keyboards & trackpads with i5, it'd cost the same as a T.
PS: 14" T-series Thinkpads are tougher than 15" models.