Energy Pro is excellent for simulating old-fashioned analog step-sequencers, ala vintage Tangerine Dream ("Rubicon" era, etc). Contrary to what was said on a review of the free version, Energy IS a sequencer (and not "just an arpegiator", even though it can be used that way), but more in the "vintage" definition of what a step-sequencer is: you have an unlimited number of patterns, variable number of steps (including odd-numbered, which is great for prog-ish odd-meter sequences), controllable glide, gate/volume for each step, and a ramp for per-step control of the filter's cutoff. To my ears the synth has a warm, punchy sound that's great for everything from vintage analog-style bass-lines (think Bill Leeb/FLA) to nice screachy lead sequences.
Current version 1.3 has improved and new synth functions (controllable waveforms for each oscillator, cross-modulation, etc), and has fixed the tempo-sync problem in SONAR that the earlier versions had. Works great in both Orion Pro and SONAR (using FXpansion's DX-VST adapter, with no crashes or glitches on my system.
What's nice is that you can trigger your sequences live on the fly via MIDI, which is perfect for generating long Tangerine-Dream-style patterns interactively.
Jorgen's email tech-support is excellent: quick and responsive.