Memory and peripheral fit for control applications
The 8 KB RAM (8K x 8) gives you room for a couple of 1 KB buffers plus stack and variables; if your application needs larger frame buffers or a TCP/IP stack, you'll want to budget carefully. The 34 I/O lines are enough to handle a keypad, an LCD character display, and a handful of sensors without an external GPIO expander.
Connectivity and analog integration
The LM3S815-EGZ50-C2T supports I²C, SPI, SSI, and UART interfaces — enough to talk to most common sensors, ADCs, displays, and serial peripherals. The Microwire compatibility on the SPI block is a nice touch if you're integrating older serial EEPROMs or interface chips. On the analog side, there's a 2-channel 10-bit ADC — not a lot of channels, but enough for a couple of analog sensor inputs or a potentiometer for user input.
Package and layout: 48-VFQFN exposed pad
If you're running the MCU near its maximum ratings or in a warm enclosure, stitch a grid of vias under the pad to the ground plane. The pad also serves as the ground return for the core — a poor thermal connection can lead to junction temperature rise and reliability issues.
That means it's safe to design into new production without worrying about an imminent obsolescence-driven redesign.