Cortex-M3 discontinued (at least for TI models)

[bigtoy]

ST is without a doubt the most "popular" Cortex processor vendor in the world. They've sold more Cortex-Mxx processors than anyone else. They also have an impressive lineup of parts.

However, they don't have everything, and depending upon your application you may want to look elsewhere. For lowest-power Cortex-M processors look at Silicon Labs. For inbult easy-to-use bootloaders look at NXP. And so forth.

"Easy to use" is deeply application dependent. A Cortex-M3 core is a Cortex-M3 core regardless of vendor. But the surrounding peripheral set, internal bootloaders (if any),  etc vary greatly. You need to define your requirements for your ideal processor first, before you can effectively go looking to find the closest match.