Energy Pro is for me the right synth at the right time. Let's examine it's two components.
As a synth there are several analog style waveforms, two oscillators, blend, several filters, LFO routings and the usual compliment of sound making tools that make for a good sounding synth, not exceptional, simply good.
As a pattern sequencer/programmable arpeggiator Energy Pro rocks. You can create your patterns on the grid which is monophonic or polyphonic. You can make the sequence shorter than the 16 steps or longer, up to 128 steps I believe. And if you want you can render your creations to .wav audio. Besides that you can program many sequences within one instance of the VSTi and do so through midi too.
If it were only a synth Energy Pro would be a decent deal at the $19 cost but with it's great pattern sequencer it's a steal. Besides that it's an awful lot of fun to work with.
There are expansion packs available, in essence saved sounds and patterns which can be found at the web site. Obviously you can save your own as well.
This, I'm hesitant to call it just a synth, this piece of kit is great for those old school electronic arpeggiations as well as anything current. The sound of Energy Pro works well with the sequencing which also lets you create a filter envelope that evolves with the sequence, there are also gate and other controls that make for highly expressive arpeggiations/sequences.
There is a synergy between the synth and sequencing engines which makes Energy Pro quite effective. It's a great tool, check out the free version to get the vibe of this instrument, it's well worth your time.