WebSphere V9 "traditional" has recently been fully Java EE 7 certified. Given the very large and loyal customer base IBM has, as well as the continued substantial usage rates for WebSphere traditional, this is sure to be a further boost to Java EE 7 adoption. In particular, it is important to note that WebSphere V9 also comes with support for Java SE 8.
WebSphere V9 joins the Java EE 7 compatible ranks of JBoss EAP 7, GlassFish 4, WildFly, WebSphere Liberty Profile 8.5, WebLogic 12.2.1, Hitachi Cosminexus, and TmaxSoft JEUS. All of the Java EE certified offerings are always listed on the official Java EE compatibility page. For some perspective, few other open standards, such as SQL, have as many available implementations as Java EE 7 already has (and this is bound to only just keep getting better).
You'll find the trial link for WebSphere V9 here. IBM senior staffer Tom Alcott has a nice technical write-up on the details of WebSphere V9 certainly including support on various cloud platforms including BlueMix. It should be noted that, unlike WebSphere traditional, WebSphere Liberty was one of the earliest available commercial Java EE 7 certified application servers, certainly well ahead of WebLogic and JBoss EAP. You should read my WebSphere Liberty Java EE 7 compatibility announcement on The Aquarium, written while I was still at Oracle.
Other than existing WebSphere traditional customers, it is difficult to recommend it over WebSphere Liberty. Liberty is definitely one of the most modular, lightweight, and impressive performing (in virtually every way) modern application platforms available today - Java EE application servers, Servlet containers, or otherwise. If you have not tried Liberty out yet, you should.